Measurements of human reaction-time have played a major role in the formulation of theories about various important metal processes underlying perception, memory, and cognition. These theories can significantly influence the resolution of important issues related to mental health. However, the theoretical interpretation of reaction-time data requires strong assumptions regarding (1) how subjects trade accuracy for speed in cognitive tasks and (2) whther there is a discrete or continuous flow of information from one component mental process to the next. Conventional reaction-time and speed-accuracy tradeoff experiments do not, by themselves, provide sufficiently powerful results to test these assumptions. The present project will help to overcome this deficiency by developing a new approach toward the collection and analysis of reaction times and errors in cognitive tasks. It relies on a novel speed-accuracy decomposition procedure which involves a mixture of regular reaction-time trials and response-signal trials where subjects produce prompted reactions before information processing has been completely finished. Through mathematical analyses of results from the procedure, one may obtain pure estimates of the amount of partial information that a person has accumulated about a test stimulus at any moment during a cognitive task. Nine experiments are proposed to validate the new procedure and analyses. The experiments deal with the nature of mental processes in word recognition and semantic-memory retrieval, two interesting test cases for the present approach. They will provide deeper insights about the rapid accumulation of partial information over time and about discrete versus continuous models of information processing, thus substantially strengthening current reaction-time methodology. Given results from the project, it may be possible to obtain better measurements of reaction time in a variety of domains relevant to mental health.